1. Field of the invention
This invention is related to watercraft boarding ladders, and in particular to a folding ladder assembly that can be hung off the side of inflatable boats or rubberized boats, for example a pontoon boat, dinghy, life raft, runabout, rescue, marine patrol, offshore work boat or comparable thin-hull watercraft, for use by divers and swimmers while boarding from open water.
2. Description of the related art
The ability to move onto a boat easily and safely is essential for obvious reasons. On the dock, a stable platform enables safe and convenient boarding alongside a boat. On open water, however, boarding is difficult and in most cases requires above average personal strength and on-board assistance as well. For this reason, most small watercraft are equipped with a boarding ladder of some kind, either permanently attached, or portable and stowed away for set-up and service as needed.
Conventional boarding ladders intended for permanent installation require a hard point load reaction structure and a substantial amount of available deck space for installation. Consequently, fixed boarding ladders are not well adapted for installation on small rubberized or inflatable boats that are subject to puncture damage. For example, a conventional pontoon boat, dinghy or a life raft has a rubberized hull that is sealed airtight and should not be pierced by fasteners. Likewise, some small runabouts or sailboats have a hull or deck made of a fiberglass material that is not capable of reacting high shear loads, thus making them vulnerable to fatigue failure and rupture.
Conventional boarding ladders of the portable kind are available in two categories: flexible (rope) ladders and rigid frame (hook) ladders. Rope ladders are easy to store and require no mounting hardware, but require exceptional physical strength to use successfully. They lack center or bottom stability and swing easily from side-to-side along the side of the hull, as well as to-and-fro beneath the hull. This makes rope ladders extraordinarily difficult to use even with on-board assistance, especially under open water conditions where the boat will be undergoing bobbing, rolling and pitching movement.
For these reasons, hook style ladders are generally preferred since they provide a stable climbing structure relative to the hull of the boat. However, the attachment of a conventional hook style boarding ladder requires a hard point reaction structure that can engage a penetrating fastener and withstand substantial shearing loads without rupture. The only hard point reaction structure available on some inflatable boats and fiberglass boats is the transom. In some smaller boats only a limited amount of space is available since the transom is almost completely occupied by an outboard motor.
Conventional boarding ladders are frequently mounted about midway along a gunnel or pontoon of small watercraft. The side mounting location may not always be available on smaller boats, since the outwardly projecting components of conventional boarding ladders may strike the dock and interfere with safe docking, or become entangled with dock rigging during docking maneuvers.
Fixed boarding ladders cannot be easily removed for storage, since they are permanently fastened to the deck and require tools for removal. Others provide only a short extension into the water, with the result that acquiring a foothold may be difficult. Other boarding ladders have included collapsible features which allow them to be reduced to compact size for storage and extended to full size for service. Those features include, for example, hinges, sliding extensions and flexible sides made of chain or rope.
Because of their construction and the desire to provide a compact assembly, conventional boarding ladders often do not provide a secure foothold below water and may not provide an adequate handhold above the water line. Using such ladders is a challenge to young persons as well as elderly, those carrying aquatic gear, such as SCUBA diving equipment or water skis, and even those persons who are in good physical condition but who may be exhausted after engaging in water sport activities, or when the ladder may be used in a man-over-board rescue emergency.
Other limitations of boarding ladders of conventional design have involved the manner in which they are attached to the boat. In particular, since compact size is generally desirable, some conventional ladders intended for marine use simply extend up to the nearest available mounting surface, for example the lower side of the gunwale. Moreover, no provision is made for quick removal and stowage when the boarding ladder is not needed.
Many conventional boarding ladders have design features that improve their usability on larger boats, especially those that are permanently fastened onto a hard deck or solid hull. However, such boarding ladders cannot be installed on inflatable, rubberized, or thin-hull vessels, which are vulnerable to piercing, puncture and rupture damage. Conventional fixed boarding ladders encroach on available deck space, and cannot be quickly or easily removed.